Build it and they will come!
Please come, I'm sure all us crashers (oopps! DD Racers0 will welcome the support.
On a sunny day Cadwell is one of those perfect places (at least if you have bikes in your blood) - but not so great when the low cloud and rain set-in.
To answer your question, spectating is prety good and you can get close to the track in many places. About 70% of the woodland circuit is visible from the grandstand (perhaps less grand and mainly stand - except you are sitting; if you see what I mean) alongside The Mountain. There is also plents of standing room alongside the track from the top of the mountain through hall bends and up to the old hairpin.
Hope you make it. Cheers.